Scavenge pump oil level control system and method

ABSTRACT

A hybrid vehicle includes a hybrid module, a transmission and a torque converter. The lubrication system associated with the torque converter includes an oil sump within the torque converter housing which is intended to be managed as a “dry” sump oil lubrication system. There is an oil pump in communication with the sump in order to manage the sump oil level. By monitoring an operational parameter of the oil pump motor (pressure, torque, or current) oil aeration can be detected.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of PCT Application No.PCT/US2012/024119, filed Feb. 7, 2012, which claims the benefit U.S.Patent Application Ser. No. 61/440,878 filed Feb. 9, 2011, both of whichare hereby incorporated by reference.

BACKGROUND

With the growing concern over global climate change as well as oilsupplies, there has been a recent trend to develop various hybridsystems for motor vehicles. While numerous hybrid systems have beenproposed, the systems typically require significant modifications to thedrive trains of the vehicles. These modifications make it difficult toretrofit the systems to existing vehicles. Moreover, some of thesesystems have a tendency to cause significant power loss, which in turnhurts the fuel economy for the vehicle. Thus, there is a need forimprovement in this field.

One of the areas for improvement is in the construction and arrangementof the hydraulic system. Hybrid vehicles, and in particular the hybridmodule associated with such a vehicle, have various lubrication andcooling needs which depend on engine conditions and operational modes.In order to address these needs, oil is delivered by at least onehydraulic pump. The operation of each hydraulic pump is controlled,based in part on the lubrication and cooling needs and based in part onthe prioritizing when one or more hydraulic pump is included as part ofthe hydraulic system of the hybrid vehicle. The prioritizing betweenhydraulic pumps is based in part on the needs and based in part on theoperational state or mode of the hybrid vehicle.

Another area for improvement within the overall hydraulics of the hybridvehicle is in the management of the oil level within the torqueconverter housing. An electric oil pump is used as a scavenge pump forthe oil sump of the torque converter housing. The scavenge pump is partof a “dry” sump oil lubrication system which requires that thecollecting oil sump pan be kept relatively dry compared to what isgenerally understood as a wet sump oil lubrication system.

One of the concerns relating to dry sump configurations and systems isoil aeration which occurs when too little oil is present in the oilsump. This is the result of excessive scavenging. Another concern is oilflooding which occurs when too much oil is present in the oil sump. Thisis the result of insufficient or inadequate scavenging. Related concernsare the monetary and energy costs associated with maintaining an oillevel sensor in the sump. The control system described herein addressesthe first two concerns by monitoring the scavenge pump and adjusting thescavenge pump performance to try and maintain a desired oil level in thesump.

SUMMARY

The hydraulic system (and method) described herein is part of a hybridmodule used within a hybrid system adapted for use in vehicles andsuitable for use in transportation system and into other environments.The cooperating hybrid system is generally a self-contained andself-sufficient system which is able to function without the need todrain resources from other systems in the corresponding vehicle ortransportation system. The hybrid module includes an electric machine(eMachine).

This self-sufficient design in turn reduces the amount of modificationsneeded for other systems, such as the transmission and lubricationsystems, because the capacities of the other systems do not need to beincreased in order to compensate for the increased workload created bythe hybrid system. For instance, the hybrid system incorporates its ownlubrication and cooling systems that are able to operate independentlyof the transmission and the engine. The fluid circulation system, whichcan act as a lubricant, hydraulic fluid, and/or coolant, includes amechanical pump for circulating a fluid, along with an electric pumpthat supplements workload for the mechanical pump when needed. As willbe explained in further detail below, this dual mechanical/electric pumpsystem helps to reduce the size and weight of the required mechanicalpump, and if desired, also allows the system to run in a completeelectric mode in which the electric pump solely circulates the fluid.

More specifically, the described hydraulic system (for purposes of theexemplary embodiment) is used in conjunction with a hybrid electricvehicle (HEV). Included as part of the described hydraulic system is aparallel arrangement of a mechanical oil pump and an electric oil pump.The control of each pump and the sequence of operation of each pumpdepends in part on the operational state or the mode of the hybridvehicle. Various system modes are described herein relating to thehybrid vehicle. As for the hydraulic system disclosed herein, there arethree modes which are specifically described and these three modesinclude an electric mode (E-mode), a transition mode, and a cruise mode.

As will be appreciated from the description which follows, the describedhydraulic system (and method) is constructed and arranged for addressingthe need for component lubrication and for cooling those portions of thehybrid module which experience an elevated temperature during operationof the vehicle. The specific construction and operationalcharacteristics provide an improved hydraulic system for a hydraulicmodule.

The compact design of the hybrid module has placed demands andconstraints on a number of its subcomponents, such as its hydraulics andthe clutch. To provide an axially compact arrangement, the piston forthe clutch has a recess in order to receive a piston spring that returnsthe piston to a normally disengaged position. The recess for the springin the piston creates an imbalance in the opposing surface areas of thepiston. This imbalance is exacerbated by the high centrifugal forcesthat cause pooling of the fluid, which acts as the hydraulic fluid forthe piston. As a result, a nonlinear relationship for piston pressure isformed that makes accurate piston control extremely difficult. Toaddress this issue, the piston has an offset section so that both sidesof the piston have the same area and diameter. With the areas being thesame, the operation of the clutch can be tightly and reliablycontrolled. The hydraulics for the clutch also incorporate a spill overfeature that reduces the risk of hydrostatic lock, while at the sametime ensures proper filling and lubrication.

In addition to acting as the hydraulic fluid for the clutch, thehydraulic fluid also acts as a coolant for the eMachine as well as othercomponents. The hybrid module includes a sleeve that defines a fluidchannel that encircles the eMachine for cooling purposes. The sleeve hasa number of spray channels that spray the fluid from the fluid channelonto the windings of the stator, thereby cooling the windings, whichtend to generally generate the majority of the heat for the eMachine.The fluid has a tendency to leak from the hybrid module and around thetorque converter. To prevent power loss of the torque converter, thearea around the torque converter should be relatively dry, that is, freefrom the fluid. To keep the fluid from escaping and invading the torqueconverter, the hybrid module includes a dam and slinger arrangement.Specifically, the hybrid module has a impeller blade that propels thefluid back into the eMachine through a window or opening in a dammember. Subsequently, the fluid is then drained into the sump so that itcan be scavenged and recirculated.

The hybrid module has a number of different operational modes. Duringthe start mode, the battery supplies power to the eMachine as well as tothe electric pump. Once the electric pump achieves the desired oilpressure, the clutch piston is stroked to apply the clutch. With theclutch engaged, the eMachine applies power to start the engine. Duringthe electro-propulsion only mode the clutch is disengaged, and only theeMachine is used to power the torque converter. In the propulsion assistmode, the engine's clutch is engaged, and the eMachine acts as a motorin which both the engine and eMachine drive the torque converter. Whilein a propulsion-charge mode, the clutch is engaged, and the internalcombustion engine solely drives the vehicle. The eMachine is operated ina generator mode to generate electricity that is stored in the energystorage system. The hybrid module can also be used to utilizeregenerative braking (i.e., regenerative charging). During regenerativebraking, the engine's clutch is disengaged, and the eMachine operates asa generator to supply electricity to the energy storage system. Thesystem is also designed for engine compression braking, in which casethe engine's clutch is engaged, and the eMachine operates as a generatoras well.

Focusing now on the torque converter portion of the HEV, the oil sump ofthe torque converter housing is constructed and arranged to be scavengedby an electric oil pump. The goal is to keep the sump of the torqueconverter housing “dry” without having excessive aeration and withoutflooding. Excessive aeration is typically the result of excessivescavenging. Flooding is typically the result of insufficient orinadequate scavenging. Instead of incurring the monetary cost and theenergy cost associated with adding an oil level sensor to the torqueconverter sump, the described control system focuses on the status andperformance characteristics of the electric oil pump.

One oil pump monitoring and adjusting option is to evaluate the pumptorque (sensed by current) and then vary the pump speed, as needed, totry and maintain the sump oil level within the desired range. Anotheroil pump monitoring and adjusting option is to vary the pump speed basedon pump torque oscillations (sensed by current readings). A stillfurther oil pump monitoring and adjusting option is to vary the pumpspeed based on the presence of pump speed oscillations.

By utilization of one of the monitoring and adjusting options, one ormore of the following benefits is expected:

-   -   1. Reduced oil aeration.    -   2. Reduced main oil sump level variation.    -   3. Sandwich sump oil level closed loop control.    -   4. Reduced spin losses.    -   5. Improved fuel economy.    -   6. Avoid excessive pressurization of downstream components.    -   7. Reduced cost (eliminates need for oil level sensor).

Further forms, objects, features, aspects, benefits, advantages, andembodiments of the present invention will become apparent from adetailed description and drawings provided herewith.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a diagrammatic view of one example of a hybrid system

FIG. 2 is a schematic illustration of the oil flow and control logicassociated with a torque converter which is a part of the FIG. 1 hybridsystem.

FIG. 3 is a graph of pump pressure versus time as a way to assess airingestion.

FIG. 4 is a graph of peak-to-peak pressure versus time as a way topresent air ingestion information.

FIG. 5 is a graph of the integration of the FIG. 4 information versustime using the slope of the line to denote air ingestion information.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the disclosure,reference will now be made to the embodiments illustrated in thedrawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of thedisclosure is thereby intended, such alterations and furthermodifications in the illustrated device and its use, and such furtherapplications of the principles of the disclosure as illustrated thereinbeing contemplated as would normally occur to one skilled in the art towhich the disclosure relates.

FIG. 1 shows a diagrammatic view of a hybrid system 100 according to oneembodiment. The hybrid system 100 illustrated in FIG. 1 is adapted foruse in commercial-grade trucks as well as other types of vehicles ortransportation systems, but it is envisioned that various aspects of thehybrid system 100 can be incorporated into other environments. As shown,the hybrid system 100 includes an engine 102, a hybrid module 104, anautomatic transmission 106, and a drive train 108 for transferring powerfrom the transmission 106 to wheels 110. The hybrid module 104incorporates an electrical machine, commonly referred to as an eMachine112, and a clutch 114 that operatively connects and disconnects theengine 102 with the eMachine 112 and the transmission 106.

The hybrid module 104 is designed to operate as a self-sufficient unit,that is, it is generally able to operate independently of the engine 102and transmission 106. In particular, its hydraulics, cooling andlubrication do not directly rely upon the engine 102 and thetransmission 106. The hybrid module 104 includes a sump 116 that storesand supplies fluids, such as oil, lubricants, or other fluids, to thehybrid module 104 for hydraulics, lubrication, and cooling purposes.While the terms oil or lubricant or lube will be used interchangeablyherein, these terms are used in a broader sense to include various typesof lubricants, such as natural or synthetic oils, as well as lubricantshaving different properties. To circulate the fluid, the hybrid module104 includes a mechanical pump 118 and an electric pump 120 incooperation with a hydraulic system 200 (see FIG. 2). With this parallelcombination of both the mechanical pump 118 and electric pump 120, theoverall size and, moreover, the overall expense for the pumps isreduced. The electric pump 120 cooperates with the mechanical pump 118to provide extra pumping capacity when required. The electric pump 120is also used for hybrid system needs when there is no drive input tooperate the mechanical pump 118. In addition, it is contemplated thatthe flow through the electric pump 120 can be used to detect low fluidconditions for the hybrid module 104. In one example, the electric pump120 is manufactured by Magna International Inc. of Aurora, Ontario,Canada (part number 29550817), but it is contemplated that other typesof pumps can be used.

The hybrid system 100 further includes a cooling system 122 that is usedto cool the fluid supplied to the hybrid module 104 as well as thewater-ethylene-glycol (WEG) to various other components of the hybridsystem 100. In one variation, the WEG can also be circulated through anouter jacket of the eMachine 112 in order to cool the eMachine 112.Although the hybrid system 100 has been described with respect to a WEGcoolant, other types of antifreezes and cooling fluids, such as water,alcohol solutions, etc., can be used. With continued reference to FIG.1, the cooling system 122 includes a fluid radiator 124 that cools thefluid for the hybrid module 104. The cooling system 122 further includesa main radiator 126 that is configured to cool the antifreeze forvarious other components in the hybrid system 100. Usually, the mainradiator 126 is the engine radiator in most vehicles, but the mainradiator 126 does not need to be the engine radiator. A cooling fan 128flows air through both fluid radiator 124 and main radiator 126. Acirculating or coolant pump 130 circulates the antifreeze to the mainradiator 126. It should be recognized that other various componentsbesides the ones illustrated can be cooled using the cooling system 122.For instance, the transmission 106 and/or the engine 102 can be cooledas well via the cooling system 122.

The eMachine 112 in the hybrid module 104, depending on the operationalmode, at times acts as a generator and at other times as a motor. Whenacting as a motor, the eMachine 112 draws alternating current (AC). Whenacting as a generator, the eMachine 112 creates AC. An inverter 132converts the AC from the eMachine 112 and supplies it to an energystorage system 134. The eMachine 112 in one example is an HVH410 serieselectric motor manufactured by Remy International, Inc. of Pendleton,Ind., but it is envisioned that other types of eMachines can be used. Inthe illustrated example, the energy storage system 134 stores the energyand resupplies it as direct current (DC). When the eMachine 112 in thehybrid module 104 acts as a motor, the inverter 132 converts the DCpower to AC, which in turn is supplied to the eMachine 112. The energystorage system 134 in the illustrated example includes three energystorage modules 136 that are daisy-chained together to supply highvoltage power to the inverter 132. The energy storage modules 136 are,in essence, electrochemical batteries for storing the energy generatedby the eMachine 112 and rapidly supplying the energy back to theeMachine 112. The energy storage modules 136, the inverter 132, and theeMachine 112 are operatively coupled together through high voltagewiring as is depicted by the line illustrated in FIG. 1. While theillustrated example shows the energy storage system 134 including threeenergy storage modules 136, it should be recognized that the energystorage system 134 can include more or less energy storage modules 136than is shown. Moreover, it is envisioned that the energy storage system134 can include any system for storing potential energy, such as throughchemical means, pneumatic accumulators, hydraulic accumulators, springs,thermal storage systems, flywheels, gravitational devices, andcapacitors, to name just a few examples.

High voltage wiring connects the energy storage system 134 to a highvoltage tap 138. The high voltage tap 138 supplies high voltage tovarious components attached to the vehicle. A DC-DC converter system140, which includes one or more DC-DC converter modules 142, convertsthe high voltage power supplied by the energy storage system 134 to alower voltage, which in turn is supplied to various systems andaccessories 144 that require lower voltages. As illustrated in FIG. 1,low voltage wiring connects the DC-DC converter modules 142 to the lowvoltage systems and accessories 144.

The hybrid system 100 incorporates a number of control systems forcontrolling the operations of the various components. For example, theengine 102 has an engine control module (ECM) 146 that controls variousoperational characteristics of the engine 102 such as fuel injection andthe like. A transmission/hybrid control module (TCM/HCM) 148 substitutesfor a traditional transmission control module and is designed to controlboth the operation of the transmission 106 as well as the hybrid module104. The transmission/hybrid control module 148 and the engine controlmodule 146 along with the inverter 132, energy storage system 134, andDC-DC converter system 140 communicate along a communication link as isdepicted in FIG. 1.

To control and monitor the operation of the hybrid system 100, thehybrid system 100 includes an interface 150. The interface 150 includesa shift selector 152 for selecting whether the vehicle is in drive,neutral, reverse, etc., and an instrument panel 154 that includesvarious indicators 156 of the operational status of the hybrid system100, such as check transmission, brake pressure, and air pressureindicators, to name just a few.

As noted before, the hybrid system 100 is configured to be readilyretrofitted to existing vehicle designs with minimal impact to theoverall design. All of the systems including, but not limited to,mechanical, electrical, cooling, controls, and hydraulic systems, of thehybrid system 100 have been configured to be a generally self-containedunit such that the remaining components of the vehicle do not needsignificant modifications. The more components that need to be modified,the more vehicle design effort and testing is required, which in turnreduces the chance of vehicle manufacturers adopting newer hybriddesigns over less efficient, preexisting vehicle designs. In otherwords, significant modifications to the layout of a preexisting vehicledesign for a hybrid retrofit require, then, vehicle and product linemodifications and expensive testing to ensure the proper operation andsafety of the vehicle, and this expense tends to lessen or slow theadoption of hybrid systems. As will be recognized, the hybrid system 100not only incorporates a mechanical architecture that minimally impactsthe mechanical systems of pre-existing vehicle designs, but the hybridsystem 100 also incorporates a control/electrical architecture thatminimally impacts the control and electrical systems of pre-existingvehicle designs.

Further details regarding the hybrid system 100 and its varioussubsystems, controls, components and modes of operation are described inProvisional Patent Application No. 61/381,615, filed Sep. 10, 2010,which is hereby incorporated by reference in its entirety.

The hybrid module 104 is generally designed to be a self-contained unitand accordingly it has its own lubrication system. When the hybridmodule 104 is coupled to the transmission 106, some leakage of the fluidinto the transmission 106 may occur. The fluid (e.g., oil) may flow intoparts of the transmission that are normally dry or absent fluid. Forinstance, fluid may flow into the area surrounding the torque converter172. As a result, the viscous nature of the fluid can slow down thetorque converter 172 and/or create other issues, such as parasitic lossand over heating of the oil. Moreover, if enough fluid exits the hybridmodule 104, an insufficient amount of fluid may exist in the hybridmodule 104, which can cause damage to its internal components.

At the interface between the hybrid module 104 and the transmission 106,the hybrid module 104 has a dam and slinger (or impeller) arrangementthat is used to retain the fluid within the hybrid module. An adapterring has a slinger blade that is designed to sling the fluid back intothe hybrid module 104. A sleeve has a dam structure that is used toretain the fluid and direct it to the sump 116. The dam structure has adam passageway positioned such that the slinger blade is able to directthe fluid through the dam passageway and subsequently into the sump 116.

Referring now to FIG. 2, a schematic diagram is provided for thedescribed monitoring and adjusting of electric oil pump 170 which isoperably connected to (i.e., in flow communication with) torqueconverter 172. The torque converter 172 receives a supply of oil forlubrication and cooling of the torque converter components and portionswithin the torque converter housing. The used and excess oil drains offand accumulates in the lower pan or sump 174 of the torque converter.The electric oil pump 170 is constructed and arranged as a scavengingpump in order to pump oil out of the sump 174 and return that oil to alarger oil reservoir 186 via conduit 176.

The level of oil in sump 174 is a factor of delivery, flow rate, and thespeed of electric oil pump 170. There are two conditions which are seenas performance issues and which should be corrected or resolved bychanging the speed of the electric oil pump. One condition or concern isdescribed as oil aeration which is the result of excessive scavenging.If the oil level is too low as scavenging continues, the electric oilpump draws in a mixture of air and oil. The other condition or concernis described as “flooding” which is the result of inadequate scavenging.Flooding is also seen as a high oil level in the torque converterhousing, i.e., in sump 174.

When oil level is relatively low, the hybrid system has the potentialfor drawing air into the intake of the pump. At moderately reduced oillevels, this can manifest itself as a localized whirlpool effect whichintroduces air gradually into the system through the intake of the oilsuction filter. The whirlpool effect is dependent on oil velocity andtemperature. Higher velocities in combination with higher viscositiespresent the biggest issue. This would most likely occur on cold start athigher engine speeds. As a result of this air induction, the entrainedair level in the oil increases. This can lead to regulator valveinstability (noisy pressure), elevated oil temperatures, longer clutchfill times, and minor shift quality issues.

At severely low oil levels the bottom of the oil suction filter isuncovered to air in a more general sense. This results in severingestion of air to the suction side of the pump. The aforementionedissues become more pronounced and there is the potential for pumppriming issues as well. Regulator valve instability can increase to thepoint of audible noise which can be heard by the operator. Elevatedtemperatures are more pronounced and can lead to transmissionoverheating.

Generally high oil levels result in oil contact with moving parts withinthe gearbox itself. With moderate overfills it results in foaming andaeration with mild increases in spin losses. This can also lead to minorincreases in oil temperature. With significantly high oil levels, thefoaming and aeration results in much higher spin losses (reduced fueleconomy) and transmission overheating. The problem tends to selfpropagate at this point. The foaming expands the oil volume and levelresulting in further foaming which leads to still higher oil levels.Eventually the foaming and aeration can result in spewing out thebreather and severe overheating.

Each condition is able to be rectified by changing the speed of theelectric oil pump 170. In the event of oil aeration, slow down the pumpspeed. In the event of flooding, increase the pump speed. The questionthen becomes how best to monitor and determine the oil level in the sumpof the torque converter. One option is to add an oil level sensor.However, this option introduces an added monetary cost and an addedenergy cost. Instead, the disclosed exemplary embodiment introducesimprovement options, each of which involve monitoring operatingparameters or conditions of the electric oil pump 170.

A first improvement option is to vary the speed of oil pump 170 based onthe torque of the oil pump which is sensed by a current reading from thepump motor. In FIG. 2, control module 178 communicates with the oil pump170 via data line 180 in order to sense the current and derive areading. This current reading is then used to determine if the speed ofoil pump 170 needs to be varied and, if so, how. The speed of oil pump170 is increased by control module 178 via data line 182 if the currentreading indicates flooding of the torque converter 172. If the currentreading indicates oil aeration, then the speed of oil pump 170 isdecreased by a signal from control module 178 via data line 182.

When the oil level is low, there is the potential for drawing air intothe intake of the scavenge pump. This air ingestion into the scavengepump may also be described as aeration. When this occurs, the pump massflow rate drops and tends to be inconsistent (noisy). One way thiseffect can be “seen” is by measuring the pressure over time. The FIG. 3graph or chart depicts one option for displaying this pressure. TheY-axis depicts “pressure” in kpa units. The X-axis is “time” in seconds.The magnitude or extent of the pressure fluctuations gives an indicationof whether or not there is any significant air ingestion by the scavengepump. While the FIG. 3 graph shows pressure versus time, torque orcurrent measurements of the scavenge pump will provide a similar displayof whether or not there is any significant air ingestion by the scavengepump.

The vehicle includes a transmission control module (TCM) which isconstructed and arranged to monitor the range of (pressure) oscillationsand calculate the peak-to-peak noise versus time. This is displayed bythe FIG. 4 graph. This graph displays the peak-to-peak pressure in kpaunits along the Y-axis and time, in seconds, along the X-axis. The TCMis capable of monitoring the peak-to-peak noise and flag aeration whenthe noise threshold exceeds a calibrated level.

The analysis can be taken a further step by integrating the FIG. 4 graphdata with respect to time. This integration result is shown by the FIG.5 graph. The slope of the line depicts the condition, noting that asteeper slope corresponds to some level of air ingestion while a flatterline of less slope corresponds to a condition of little or no airingestion by the scavenge pump.

The FIG. 5 graph provides a clear distinction, based on the slope of theline, of when air is ingested (the steeper slope) and when no noticeableamount or volume of air is ingested (the flatter slope). By calibratingthe slope and establishing a reference table (or using one alreadycreated), a measurement of the slope of the FIG. 5 graph line will yieldthe level (i.e., the amount or volume) of air ingested by the scavengepump. Relative measures are given in Table I which corresponds to FIG.5.

TABLE I Integration Air Slope Entrainment 0.2 <2%  0.3 3% 0.4 4% 0.5 5%0.6 6% 0.7 >7% 

As noted above, the data displayed in the graphs of FIGS. 3-5 is basedon pressure readings and the peak-to-peak pressure readings. However, inlieu of using pressure, scavenge pump torque measurements will provide asimilar response and way to assess air ingestion (i.e., aeration). Thesame is true for scavenge pump current measurements. Depending on theexistence or level of any oil aeration (i.e., air ingestion), the speedof the oil pump 170 can be varied. Ideally for a “dry” sump, the oillevel will be managed such that it is controlled at the point whereaeration might just start. If that is not indicated, then increase thepump speed. Once aeration is detected, then slow the speed of the pump.This somewhat continual adjusting of the pump speed is one way to keepthe oil level at the threshold of aeration which is a suitable way tomanage a “dry” sump. Referring to FIG. 2, the control module 178communicates with the oil pump 170 via data line 182. Readings from theoil pump motor are received by the control module via data line 180.These connections are important in order to obtain the data and controlscavenge pump operation.

By controlling the scavenge pump speed through the monitoring of thepump motor and/or the monitoring of pump pressure fluctuations oroscillations or torque oscillations and/or speed oscillations, one ormore of the following benefits is to be expected:

-   -   1. Reduced oil aeration. This results in better cooling,        improved valve stability, and improved shift quality.    -   2. Reduced main oil sump level variation. This results in less        oil volume required, thereby reducing cost and weight.    -   3. Sandwich sump oil level closed loop control. This eliminates        the need for a separate oil sump in the hybrid motor housing,        thereby reducing cost and complexity.    -   4. Reduced spin losses. This results in lower cool temperatures        (improved reliability) and improved fuel economy.    -   5. Improved fuel economy. This results in lower operator costs        and improved sales.    -   6. Avoid excessive pressurization of downstream components. This        is achieved by reducing the noise associated with excessive        aeration. The hydraulic components will see less fatigue stress        and thereby provide longer operational life.    -   7. Reduced cost (eliminates the need for an oil level sensor).        Also there is the option of eliminating a separate sump, oil        pump, regulator valve, etc.

While the preferred embodiment of the invention has been illustrated anddescribed in the drawings and foregoing description, the same is to beconsidered as illustrative and not restrictive in character, it beingunderstood that all changes and modifications that come within thespirit of the invention are desired to be protected.

1. An oil level control system for an oil sump of a hybrid electricvehicle, said oil sump including a supply of oil with an oil level, saidoil level control system comprising: an electric oil pump constructedand arranged in fluid communication between said oil sump and an oilreservoir, said electric oil pump being constructed and arranged to pumpoil from said oil sump to said oil reservoir to lower the oil level ofsaid sump; and a control module constructed and arranged in electricalcommunication with said electric oil pump for controlling the operationof said electric oil pump, said control module being programmed with anacceptable oil level range, said acceptable oil level range being basedon an electric oil pump parameter, wherein said electrical oil pump isoperated as required to maintain said oil level of said oil sump withinsaid acceptable oil level range.
 2. The oil level control system ofclaim 1 wherein said electric oil pump parameter is a pump torquereading of said electric oil pump.
 3. The oil level control system ofclaim 2 wherein said electric oil pump torque reading is sensed bytaking a current reading.
 4. The oil level control system of claim 1wherein said electric oil pump parameter is a torque oscillation of saidelectric oil pump.
 5. The oil level control system of claim 4 whereinsaid electric oil pump torque oscillation is sensed by taking a currentreading.
 6. The oil level control system of claim 1 wherein saidelectric oil pump parameter is a pump speed oscillation of said electricoil pump.
 7. The oil level control system of claim 1 wherein said oilsump is part of a torque converter.
 8. A method of adjusting an oillevel of an oil sump of a hybrid electric vehicle, said oil sumpincluding a supply of oil, said method of adjusting comprising thefollowing steps: (a) providing an electric oil pump; (b) constructingand arranging said electric oil pump in flow communication between saidoil sump and an oil reservoir; (c) providing a control module; (d)constructing and arranging said control module in electricalcommunication with said electric oil pump; (e) sensing a parameter valueof said electric oil pump; (f) comparing said sensed parameter value toan acceptable range for said parameter, said acceptable rangecorresponding to an acceptable oil level range; and (g) operating saidelectric oil pump as necessary to maintain the oil level of said oilsump within said acceptable oil level range.
 9. The method of adjustingof claim 8 wherein said sensing step includes sensing a pump torquereading of said electrical oil pump.
 10. The method of adjusting ofclaim 8 wherein said sensing step includes sensing a torque oscillationof said electric oil pump.
 11. The method of adjusting of claim 8wherein said sensing step includes sensing a pump speed oscillation ofsaid electrical oil pump.
 12. The oil level control system of claim 2wherein said oil sump is part of a torque converter.
 13. The oil levelcontrol system of claim 3 wherein said oil sump is part of a torqueconverter.
 14. The oil level control system of claim 5 wherein said oilsump is part of a torque converter.
 15. The oil level control system ofclaim 6 wherein said oil sump is part of a torque converter.
 16. Aliquid control system for managing a liquid level within a supplylocation, said liquid control system comprising: a liquid pumpconstructed and arranged in fluid communication between said liquidsupply location and a transfer location, said liquid pump beingconstructed and arranged to pump liquid from said liquid supply locationto said transfer location to lower the liquid level of said liquidsupply location; and a control module constructed and arranged inelectrical communication with said liquid pump for controlling theoperation of said liquid pump, said control module being programmed withan acceptable liquid level range, said acceptable liquid level rangebeing based on a liquid pump parameter, wherein said liquid pump isoperated as required to maintain said liquid level of said liquid supplylocation within said acceptable liquid level range.
 17. The liquidcontrol system of claim 16 wherein said liquid pump parameter is a pumptorque reading of said liquid pump.
 18. The liquid control system ofclaim 17 wherein said liquid pump torque reading is sensed by taking acurrent reading.
 19. The liquid control system of claim 16 wherein saidliquid pump parameter is a torque oscillation of said liquid pump. 20.The liquid control system of claim 16 wherein said liquid pump parameteris a pump speed oscillation of said liquid pump.